Podcast
Questions and Answers
What are the two general classes of polymers?
What are the two general classes of polymers?
- Amorphous and crystalline
- Thermoplastics and thermosets (correct)
- Linear and branched
- Addition and condensation
What happens to the melting point as molecular weight increases?
What happens to the melting point as molecular weight increases?
increases
As the degree of branching increases, what happens to density?
As the degree of branching increases, what happens to density?
decreases
What is a plastic that has two monomers in its molecular structure called?
What is a plastic that has two monomers in its molecular structure called?
A polymer in which the chains are highly ordered is said to be:
A polymer in which the chains are highly ordered is said to be:
What is the term for a polymer with essentially random chain arrangement?
What is the term for a polymer with essentially random chain arrangement?
The stiffer HDPE is associated with what kind of molecular weight?
The stiffer HDPE is associated with what kind of molecular weight?
What is the molecular structural difference between HDPE, LDPE, and LLDPE?
What is the molecular structural difference between HDPE, LDPE, and LLDPE?
What is the process of improving properties of plastic film by stretching in one or two directions called?
What is the process of improving properties of plastic film by stretching in one or two directions called?
LLDPE stands for?
LLDPE stands for?
PP stands for?
PP stands for?
PS stands for?
PS stands for?
PVC stands for?
PVC stands for?
EVOH stands for?
EVOH stands for?
PA stands for?
PA stands for?
PET stands for?
PET stands for?
PVDC stands for?
PVDC stands for?
OPP stands for?
OPP stands for?
PVAC stands for?
PVAC stands for?
What is a distinguishing feature of a polymer with lower crystallinity compared to one with higher crystallinity?
What is a distinguishing feature of a polymer with lower crystallinity compared to one with higher crystallinity?
How do the general properties of thermoplastics and thermosets differ?
How do the general properties of thermoplastics and thermosets differ?
What properties of plastics are affected by the molecule's degree of polarity?
What properties of plastics are affected by the molecule's degree of polarity?
How are heat-shrink properties imparted to a polymer?
How are heat-shrink properties imparted to a polymer?
What is cold flow?
What is cold flow?
Why are all plastics clear in the melt state?
Why are all plastics clear in the melt state?
Which two common packaging plastics are predominantly nonpolar?
Which two common packaging plastics are predominantly nonpolar?
From what raw material source are most packaging plastics made?
From what raw material source are most packaging plastics made?
What is the purpose of flame or corona treatment?
What is the purpose of flame or corona treatment?
Which has the higher melting point: high-molecular-weight polysulfone or low-molecular-weight polysulfone?
Which has the higher melting point: high-molecular-weight polysulfone or low-molecular-weight polysulfone?
What is the purpose and advantage of producing copolymers?
What is the purpose and advantage of producing copolymers?
Study Notes
Polymer Classes
- Two main types of polymers: thermoplastics and thermosets.
- Thermoplastics are widely used in packaging; they can reshape upon heating.
- Thermosets have cross-linked structures and remain fixed once set, unable to be reshaped.
Molecular Weight and Properties
- As molecular weight increases, melting point also increases.
- Higher molecular weight in HDPE results in increased stiffness.
Structural Characteristics
- Increased branching in polymer molecular structure leads to decreased density.
- HDPE features linear chains, while LDPE has highly branched chains, and LLDPE possesses short, branched chains.
Polymer Conformation
- Polymers can be crystalline with ordered chains, or amorphous with random arrangements.
- Crystalline polymers tend to have higher density and lower clarity compared to amorphous types.
Orientation and Stretching
- Orientation of polymer molecules through stretching enhances properties by aligning them along the stress direction.
Common Polymers and Their Acronyms
- LLDPE: Linear low-density polyethylene
- PP: Polypropylene
- PS: Polystyrene
- PVC: Polyvinyl chloride
- EVOH: Ethylene-vinyl alcohol
- PA: Polyamide
- PET: Polyethylene terephthalate
- PVDC: Polyvinylidene chloride
- OPP: Oriented polypropylene
- PVAC: Polyvinyl acetate
Physical Properties and Applications
- Clarity is generally lower in more crystalline polymers compared to amorphous ones.
- Thermosets are designed for higher use temperatures and solvent resistance.
Influence of Polarity
- Polarity affects melting point, solubility, barrier properties, and coefficient of friction in plastics.
Heat and Cold Flow
- Heat-shrink properties are developed through specific thermal and mechanical processing.
- Cold flow, or "creep," is crucial in applications where plastics bear significant loads.
Behavior in Melt State
- All plastics appear clear in their melt state due to the rapid motion of molecules, preventing any structured arrangement.
Material Sources
- The majority of packaging plastics originate from petrochemical sources.
- Common packaging plastics like polyethylene and polypropylene are predominantly nonpolar.
Surface Treatment
- Flame or corona treatment enhances surface polarity, improving adhesion properties for low-polarity plastics.
Melting Points of Polymers
- High molecular weight polysulfone exhibits a higher melting point compared to lower molecular weight counterparts.
Copolymers
- Copolymers combine the beneficial properties of different polymers, allowing for improved material performance.
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Description
Test your understanding of polymer chemistry as presented in Chapter 10. This quiz focuses on the two main classes of polymers, their applications in packaging, and their molecular structures. Perfect for nonchemists looking to deepen their knowledge in this area.
